What is the difference between the Pentium and Pentium Pro?

The Pentium III is an x86 (more specifically, an i686) architecture microprocessor by Intel, introduced on February 26, 1999. Initial versions were very similar to the earlier Pentium II, the most notable difference being the addition of SSE instructions and the introduction of a controversial serial number which was embedded in the chip during the manufacturing process. As with the Pentium II, there was also a low-end Celeron version and a high-end Xeon version. The Pentium III was eventually superseded by the Pentium 4. An improvement on the Pentium III design is the Pentium M.